The present invention relates to implantable heart-assist devices, specifically heart assist devices including extra-aortic balloon (EAB) pumps for providing assistance to an active heart. The present invention is particularly related to EAB pumps used in conjunction with an internal fluid pump, such as a fluid filled bladder/skeletal muscle pouch type pump such as that disclosed by Stephenson et al. (U.S. Pat. No. 4,979,936), further referenced hereinbelow.
Heart-assist devices are well known in the art. Leachman, Jr. (U.S. Pat. Nos. 3,911,897 and 3,911,898) disclose a heart-assist device including a blood pump which is connected serially between a heart ventricle and the vascular system. During normal operation, the pump is used to maintain a programmed pressure at the ventricle discharge during systolic cardiac pulsation. A pressure transducer detects the pressure at the discharge and controls the pump through a hydraulically powered, closed-loop servomechanism.
Poirier (U.S. Pat. Nos. 4,023,468 and 4,133,616) disclose a blood pump stroke volume limiter for use with a collapsible wall blood pump system. The nomadic pump is adapted primarily as a left ventricle heart-assist device and has a flexible bladder within a rigid housing. A nomadic driver applies rhythmic pulses between the bladder and the housing to repetitively collapse the bladder and establish a pumping action through the bladder, in conjunction with check valves in the inlet and outlet to the bladder. Robinson et al. (U.S. Pat. No. 4,240,409) disclose a circulatory assist device including a valveless pump with a flexible bladder. A pneumatic driver similar to that disclosed by Poirier in U.S. Pat. Nos. 4,023,468 and 4,133,616, and a flexible conduit for conveying blood between the patient and the pump. Preferably, in use, the pump and driver are mounted to the patient's body.
Solonina (U.S. Pat. No. 4,704,120) discloses a one-piece prothesis for biventricular cardiac assistance and reanimation which is preferably implanted in the right hemithorax between the diaphragm and the right lung. The prothesis includes a one-piece shell and two blood circulating deformable-diaphragm pumps actuated by fluid, preferably a compressed gas.
Kolff (U.S. Pat. No. 4,838,889) discloses a ventricle assist device including a housing an atrial chamber, an atrial compliance chamber, a ventricle chamber and a ventricle pumping chamber. A pumping member within the housing separates the ventricle blood chamber from the ventricle pumping chamber and is displaced by a drive fluid to expel blood out of the ventricle blood chamber through an outlet port.
Wampler (U.S. Pat. No. 4,906,229) discloses a high-frequency transvalvular blood pump preferably for temporary cardiac assist which provides suction to decompress the ventricle cavity during both systole and diastole. The intake end of the pump is preferably connected to a cannula which is inserted into the ventricle cavity through the aortic valve. The pump consists of a stiff barrel whose interior volume can be alternately reduced and expanded by a flexible membrane preferably controlled by pneumatic pressure from an extracorporeal location through a percutaneously inserted lumen.
Jarvik (U.S. Pat. No. 4,938,766) disclose a plurality of representative prosthetic arterial compliance chambers (PACCs). In principle, a PACC device is disclosed to be a blood containing chamber that changes in volume as a function of a pressure which is applied. The devices disclosed include, but are not limited to, a generally rigid device such as a cylinder with a spring loaded piston, an elastic device such as a stretchable balloon, or a resilient deformable device such as a flattened tube. Jarvik teaches that the device must be connected to a blood vessel and designed to avoid blood damage and thrombosis.
It will be appreciated that Jarvik's concern about avoiding blood damages and thrombosis are concerns shared by all of those skilled in the art of providing heart-assist devices. It will be further appreciated that this is presently an area of significant experimentation and that damage to the blood and unnatural movement of blood fluids through a heart-assist device may result in thrombosis and other life-threatening events.
Khalafalla (U.S. Pat. No. 4,813,952) discloses a muscle-powered pump to assist an active heart. The device comprises an oblate, spheroidal-shaped pumping chamber surrounded by innervated skeletal muscle tissue and can be coupled to a ventricle and the descending aorta with valves stimulated in synchrony with the natural depolarization of the heart, or inserted into the descending aorta and used as a counterpulsation device. Of the configurations for counterpulsation, one employs an essentially blind-ended pumping chamber which would be likely to present a high risk for causing thrombosis, because blood could be expected to stop flowing momentarily in the dead space at the end of the chamber when the muscle tissue is not contracting. Another utilizes skeletal muscle tissue wrapped directly around the aorta. This would present problems following surgical implementation, because there is very little space on the aorta around which to wrap the skeletal muscle without disrupting the flow of blood to the spinal cord through the numerous vertebral branches of the aorta. If it is necessary to ligate any of the vertebral branches, a significant risk of subsequent paraplegia is created.
Stephenson et al. (U.S. Pat. No. 4,979,936) disclose a heart-assist apparatus including an innervated skeletal muscle pouch which surrounds a collapsible, shape-retaining bladder. The bladder is interconnected to a second bladder enclosed in a sheath around a portion of the descending aorta. The bladders are filled with a fluid such that when the skeletal muscle contracts in response to an electrical stimulation, the fluid is forced from the first bladder to the bladder sheathed with the aorta, expanding that bladder and forcing the aorta to compress. Although quite creative, limited access to the aorta due to the numerous vertebral branches still presents a problem. It will be appreciated, therefore, that there continues to be a need for heart-assist devices which can be employed without creating risks for heart-assist devices which can be employed without creating risks for thrombosis, paraplegia or other potentially debilitating or life threatening conditions.
All of the heart-assist devices disclosed hereinabove are believed to devices for which experimentation is either continuing or under further evaluation. It will be appreciated that the complexities of cardiac implantation, vascular thrombosis and vascular fluid mechanics continue to have uncertainties which require further experimentation and understanding before settled procedures for providing safe and reliable assistance to the active heart will be available to medical practitioners and the public.
In this context, the present invention is directed to an extra-aortic balloon pump which improves upon the teachings of the prior art disclosed above, and addresses further problems associated with heart-assist devices and other related devices and methods, and solves other problems associated therewith.